1. Field of the Invention
This invention relates to decoy flares. More particularly, this invention relates to infrared decoy flares.
2. Description of the Prior Art
Since the introduction of compositions based on the magnesium-fluorocarbon in 1959, infrared (IR) decoy flares have utilized this energy source. In the next 20 years, the use of seekers which can use two-color discrimination, area versus point source discrimination or other flare discriminators is anticipated. These seekers cannot be decoyed with the currently used magnesium-Teflon composition despite its intensity.
Many attempts have been made in the past two decades to increase the intensity of IR decoys and to modify the spectral distribution of the radiation they emit. These attempts have not met with significant success. The reports on these attempts make it evident that the work has been based on schemes to modify or increase the mass flow rate, the energy of the chemical reaction or the emitting species. While a large increase in radiance can be achieved either by a modest temperature increase or by a proportional increase in the radiating area, another largely ignored method for increasing the intensity depends on increasing the efficiency with which the flare flame is utilized as a source of radiant energy. One way in which this can be done is by insuring that the optical thickness of the flame is optimum.
Another largely neglected concept is that intensity may be increased by increasing the area of the pyrotechnic flame. One exception to this neglect is the xe2x80x9cRoman Candlexe2x80x9d concept of expelling flaming gouts of fuel. When this is done, effectively the radiating area is increased and, thus, the radiant energy presented to a seeker is also increased. However, this concept has only been partially successful. The implementation of it has inherent problems which have made its ultimate application to high-speed aircraft, especially in afterburner, of dubious utility.
This invention is based on what may conveniently be called a pyrotechnic pellet concept. The concept applies both of the aforementioned neglected concepts, i.e., increased radiating flare area and optimization of the optical thickness of the flare, and pyrotechnic pellets are no more restricted than conventional flares insofar as utilization by high-speed aircraft is concerned. Essentially, this invention involves the replacement of a large single grain of pyrotechnic material with a multiplicity of smaller pellets which will burn at different rates to allow tailoring of the intensity-time profile.